Canada

Fingers crossed because most battlegrounds would be in blue states. I hope that if he tries to force blue states to fight their neighbors, those states would rather secede and fight back

The strategic situation favors the US immensely, with all our cities situated directly on the border. There's basically no way to mount any kind of serious defence of Canada. Every city, almost every strategically valuable location, would be lost in days.

But our nation is superbly suited to guerilla warfare, with our vast forests providing excellent cover against aerial and satellite observation, and the CAF is superbly good at fighting against superior numbers and firepower because they train around the assumption that they will be fighting an enemy that outclasses them in equipment and numbers. Manuever warfare, hit and run strikes and defeat in detail are core to CAF tactics, and they know how to fight in ways that maximize their impact while minimizing losses.

They're also very, very good at what they do. Canadians routinely demolish Americans in wargames and training operations. Our training standards are much higher and it bears results. This isn't much help against the sheer scale of the American military; a holding action like the one Ukraine is putting up against Russia would be functionally impossible. But a guerilla war would make the Americans pay a heavy toll for every day they tried to remain here.

The US would control the cities, but all of those strategic resources that Trump wants are deeper in the interior and much more vulnerable to hit and run attacks by a determined Canadian military presence, while ordinary resistance fighters would be able to launch terror strikes against vulnerable targets all across the continental US. They would have to place security forces everywhere, while we can choose to strike anywhere. Just the financial and political weight of protecting every state capitol, every senators home, every factory, every distribution centre, every power plant... Hell, every mall and school if we want to go that far... Would be absolutely crushing. How long would the American people put up with going through checkpoints to get to work, being pulled over and searched my soldiers to get to the grocery store, all while watching bombs blow up in their neighbourhoods and their tax dollars get pissed away on the world's largest and most expensive national security operation? America is swimming in debt and piling on more to give tax breaks to billionaires, and a right wing government has no way to embrace the kind of radical economic thinking that could try to solve those problems. How long could they even sustain an occupation for?

We need to take cues from Ukraine and work on a drone airforce and navy.

Get millions of the things.

We have the robotics capability to lead the world in this.

But personally I believe the US would descend into civil war before this happens

Which doesn’t mean we shouldn’t prepare for this possibility, starting yesterday.

We can use the money we were pissing away on F35s to create a national corps, who would be trained in the types of guerrilla warfare we’d need in this scenario. And be cross-trained to respond to climate emergencies such as floods and hurricanes and fires. And help build out infrastructure to shore up our east-west corridors and access to the north.